Nuclear Science Merit Badge:

Radiation Health & Safety

Nuclear Science Merit Badge:

Radiation

• Types of Radiation

• Consequences of exposure to radiation

• Uses in the medical field

• Radiation containment

Learning Objectives

• Radiation is the process in which energetic particles or waves travel through a medium or space.

• Generally refers to electromagnetic (EM) radiation (charged particles)

• Examples: Sunlight, Microwaves, Sound waves (non-EM)

What is Radiation?

Types of EM Radiation

• Non-Ionizing – Radio waves– Visible light– Microwaves

• Ionizing– X-rays– Gamma rays

Ionizing Radiation

• Ionization is caused when an electron is added to or removed from an atom.

• Ionizing radiation is radiation that has sufficient energy to strip electrons from atoms, thus making them ions.

• The remaining positively charged atom and the free electron are called “ion pairs.”

• An X-ray is a type of ionizing radiation that has a wavelength in the range of 0.01 to 10 nanometers.

• A Gamma ray is a type of ionizing radiation that has higher energy than X-rays and has a wavelength less than .01 nanometers.

• Concrete or lead are needed to shield against these radiations

Ionizing Radiation

Electroscope

History Behind Radiation

• X-rays were first discovered

by Wilhelm Roentgen in

1895.

• He noticed how the rays

could pass through some

materials and not others.

• The rays could be detected

using a photographic plate

• Henri Becquerel discovered that

uranium caused a photographic

plate to be fogged, just like X-

rays.

• In 1898, Marie Curie gave this

property the name radioactivity.

• Radioactivity is the tendency of

an element to give off charged

particles or rays (i.e., to emit

energy).

History Behind Radiation

• Two charged particles that are emitted by a radioactive element are Alpha (α)

particles Beta (β)

particles

Charged Particles

• An alpha particle has two protons and two neutrons Same as He2+

Mass: 4 AMU No electrons!

Charged Particles

• A beta particle is an electron or a positron. Electron charge:

-1 e Positron charge:

+1 e

Charged Particles

• A cloud chamber can be used to track the path of electrically charged particles.

• When a magnetic field is applied it is able to identify the charge and velocity of the particle.

• Cloud Chamber Video

Cloud Chamber

Radioisotopes

• Isotopes of an atom that are radioactive are called radioisotopes.

• These atoms are radioactive because they have too much energy to be stable; they will release energy until they become stable.

• This is called radioactive decay. The modern words are “spontaneous nuclear transformation.”

• In the process of radioactive

decay, an atom actually

changes from one element to

another by changing its

number of protons.

• The half-life of a radioactive

substance is the amount of

time required for it to lose one

half of its radioactivity and

transform into another

element.

Radioactive Decay

Activity Time!!

Let’s demonstrate half-life using a piece of paper!

Radioactive Decay

• Radioactivity (or “activity”) is measured in units of:– “curie”

• Ci• Defined as 3.7 x 1010 decays per second• The traditional unit

– “becquerel”.• Bq• Defined as 1 decay per second• The SI unit

• Alpha decay– Nucleus emits an α

particle– Loses 2 protons, 2

neutrons

• Beta decay– Nucleus emits a β

particle– Converts a neutron

into a proton and an electron (i.e., the beta particle)

Types of Radioactive Decay

Examples

Half life = 5.2 years

Half life = 4,468,000,000 years

• colbolt-60 that is used in cancer therapy, decays to nickel-60 with loss of a β particle.

•radioactive decay of Uranium-238 by alpha emission.

Radiation Hazards and Safeguards

• The international radiation symbol (also known as trefoil) first appeared in 1946, at the University of California, Berkeley Radiation Laboratory.

• At the time, it was rendered as magenta with a blue background.

• The modern version is black against a yellow background

The International Radiation Symbol

Why should ionizing radiation be controlled?

• Ionizing radiation can damage living tissue in the human body.

• It can create reactive molecules that are poisons in the body.

Acute (Deterministic) Radiation Effects

• Acute radiation symptoms are caused by high levels of radiation usually over a short period of time

• They cannot be predicted with certainty.

• Examples: erythema (redness of the skin) and epilation (hair loss)

Chronic (Stochastic) Radiation Effects

• Chronic radiation symptoms are caused by low-level radiation over a long period of time.

• Effects are based on probabilities.

• Exposure to low levels of radiation increase a person’s chances to get cancer.

0.62 rem/y – average annual radiation exposure in the U.S.

2 rem/y – international radiation exposure limit

5 rem/y – current US NRC radiation exposure limit

25 rem – measureable blood changes

100 rem – onset of radiation sickness

Radiation Exposure Levels & Effects

Radiation Exposure Levels & Effects

200 rem – radiation sickness with worse symptoms in less time

400 rem – approximately the lethal dose for 50% of the population in 30 days

1,000 rem – death probable within about 2 weeks, effects on the gastrointestinal tract

5,000 rem – death probable within 1-2 days, effects on the central nervous system

Nuclear Technologies

• Radiology: X-ray imaging.

• Nuclear Medicine: Following radioactive tracers in the body.

• Radiation Therapy: for the treatment of cancer

Radiation in Medicine

http://www.missouristate.edu/assets/HPER/rib_x-ray.jpg

• External beam

treatments

• Radionuclide

treatments

(brachytherapy)

Radiation Therapy

• Radiation used to kill pests, preserve harvested crops.

• Helps detect level of pollution and fertilizer in crops.

• Delay sprouting and spoilage

Radiation in Agriculture

• Process control using radiation gauges

• Check for leaks in underground pipes.

• Control thickness of manufactured materials

Radiation in Industry

http://www.gcsescience.com/Thickness-Control-Radioactivity.gif

• X-ray checks of baggage

• Whole-body scanners

of passengers

• Smoke detectors in homes and offices

Radiation in Security

• Mars rovers• Satellites• International Space

Station• Deep-space Probes• Radioisotope

Thermoelectric

Generators (RTG)

Radiation in Space

• Radiocarbon Dating – Carbon-14

• Neutron activation - “Finding a needle in a haystack”

• Engine testing

Radiation in Science

Differences in dose types

Thought experiment

• Alpha particles do MUCH more biological damage with a given amount of dosage than gamma rays.

• Why?

Answer

• Gamma rays penetrate straight through virtually any material, including tissue, while alpha particles are easily stopped by thin barriers, including human skin.

• Alpha particles will thus deposit their energy into a human much more readily than gamma rays, resulting in more tissue damage.

Typical Radiation Detectors

• Film packet

• Thermoluminescent Dosimeter (TLD)

• Ionization chamber

• Geiger-Müller (GM) Detector

• Scintillation Detector

Radiation Kit

• How does distance effect the measurement of radiation?

• How does shielding effect the measurement of radiation?

• How does time effect the measurement of radiation?

Thought experiment 2

Answer

• With increasing distance the radiation dose rate drops since the concentration of particles decreases

Answer #2

• Shielding reduces the amount of radiation that reaches you, reducing the dose rate

Answer #3

• A shorter time period doesn’t reduce the dose rate, however since you’re exposed to the source for less time you receive less dose.

• Background Radiation is radiation that is a

natural part of our environment.

– Rocks and soil

– Cosmic radiation

– Solar radiation

– Radon gas

– Food and water• From human made sources

– X-ray machines

– Other medical uses

– Tritium dial wristwatches

– Gas lantern mantles

– Smoke detectors

Background Radiation

• ALARA- As Low As Reasonably Achievable

• Time, Distance, and Shielding

• National and International limit – 5 rem/y (5000 mrem/y)

• Public limit – 100 mrem/y• Radiation Hazard symbol

– Displayed at places where radioactive materials are used and stored.

Radiation Regulations

ALARA SCENARIOS

• Types and effects of Radiation• Uses of radiation• Consequences of exposure• Containment techniques

What we learned

American Nuclear Society